This invention relates to apparatus for evenly distributing an electron flux emitted from cathode electrodes on an anode electrode.
In an electronic device, for example, a flat, fluorescent display tube, electrons emitted from cathode electrodes are caused to impinge upon an anode electrode coated with a phosphor through a character selection grid electrodes to cause the phosphor to luminesce, but as the area of the phorphor film increases, it becomes difficult to evenly discribute the electron flux over the entire area, thus causing dark and bright portions. For this reason, it has been the practice to interpose auxiliary electrodes between the cathode electrodes and the anode electrode, and by using a special construction for the auxiliary electrode or by applying a positive potential upon the auxiliary electrode with respect to the cathode electrode, the electron flux distribution on the anode electrode was improved to some extent. However, these measures are not yet sufficient to perfectly prevent uneven luminescence of the phosphor film.